I am working with 2 rasters, having different extents but same coordinate system and resolution, in Arcgis 10.5. The larger raster has 0 and smaller raster has 1 values. I want to make a new raster such that smaller raster boundary has 1 value and rest of the boundary in larger raster has 0. I have set the null values as 0.

raster 1 (larger extent) + raster 2 (smaller extent) results in raster 2 (smaller extent). I set extent as raster 1 in settings.

Could you suggest me what's wrong?

3 Answers 3


If you set your environment extent correctly to raster 1, then the extent of the output raster will be that of raster 1, but you will only get data where raster 2 has data (because Value + NoData == NoData).

You can use the CellStatistics tool, with the Sum option and Ignore NoData set to "DATA" with the environment extent set to raster 1

  • you are a rockstar! your suggestion of cellStatistics helped me! had 2 different sized raster
    – Gero
    May 22, 2023 at 0:58

I have always had a hard time trying to get rasters of differing spatial extents to output to the "Union of Inputs".

You could try setting this up first before trying the steps outlined below. First try to set the processing extent to "Union of Inputs". If that does not work, try this.

You can use the "Mosaic to New Raster" process. Make sure Raster 2 is at the top of the list and the "Mosaic Operator" is set to "FIRST".

  • Thank you. Union of inputs results in an error. However, "Mosaic to New Raster" works well.
    – Santosh
    Oct 8, 2018 at 6:39

If you set the extent to raster1 image, then you can use Con with IsNull functions to convert the Null data of your output raster to 0 as follows:


The output will convert Null data to 0 of your output raster.

  • Thank you. "Mosaic to New Raster" suggested by Keagan Allan worked.
    – Santosh
    Oct 8, 2018 at 22:27

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